Powdered polymer products are presently produced by various complex and expensive procedures. These generally require an initial monomer polymerization in a reaction vessel, in a suitable vehicle. After evaporation of the vehicle to produce a solid polymer, the polymer is generally then compounded in various mixing apparatus, subsequently cooled, and then ground to a powdered product of a desired particle size. Such procedures are obviously quite complex and expensive, and methods for short-cutting this procedure have been sought for a considerable period of time.
In addition, various methods have been utilized to polymerize coatings of various polymerizable organic compounds utilizing irradiation with high energy electrons to effect such polymerization. Thus, Turner U.S. Pat. No. 3,440,084 discloses a process for coating electrically conductive objects employing a gaseous coating material, and simultaneously curing that coating employing radiation-curable coating compositions, such as paints, varnishes, and the like. In that patent, the vaporized organic coating acquires a negative electrical charge upon entering an electron beam, and then is electrostatically deposited upon the work piece constituting a positive electrode. Electrons of polymerization-effecting energy are then directed on the work piece and the coating is cured thereby.
Waddington U.S. Pat. No. 3,013,957 discloses the exposure of a polymerizable material to high energy radiation in the presence of a blowing agent to decompose the blowing agent. In this process, however, the invention is not directed to polymerizing using high energy radiation, but there is a disclosure to the effect that the process of that invention enables desired effects to be achieved with materials which polymerize when irradiated.
Wright U.S. Pat. No. 3,635,750 relates to preparing polymer coatings on a substrate by simultaneous ultra-violet surface photopolymerization. In addition, Schmitz et al. U.S. Pat. No. 2,921,006 teaches polymerization of certain monomers by irradiating with high energy electrons, i.e., in the form of a solution or emulsion.
Furthermore, Dewey et al. U.S. Pat. No. 2,892,946 teaches the bombardment of gas phase systems with high energy charged particles, which are deflected with a magnetic field in order to cause chemical reactions therein for various purposes.
Finally, various apparatus has been developed for generating an electron beam curtain for a number of purposes. Thus, Sims U.S. Pat. No. 3,612,941 and Denholm et al. U.S. Pat. No. 3,769,600, both assigned to Energy Sciences, Inc. of Bedford, Mass., relate to such apparatus. These patents teach that such energetic electron beam curtains may be used for processing materials such as the curing of metal coatings, cross-linking of plastics, the sterilization of materials, etc.
Each of the above-noted techniques and apparatus for obtaining polymerization in various systems have met with varying degrees of success, but the search has continued for a simple and efficient system whereby polymerized powdered products may be produced.